Around 150-200 million people around the world are chronically infected with Hepatitis C virus (HCV). The infection can cause liver inflammation (hepatitis) that is often asymptomatic, but ensuing chronic hepatitis can result later in cirrhosis (fibrotic scarring of the liver) and liver cancer.
The hepatitis C virus (HCV) is spread by blood-to-blood contact with an infected person's blood. The symptoms can be medically managed, and a proportion of patients can be cleared of the virus by a long course of anti-viral medicines. Although early medical intervention is helpful, people with HCV infection often experience mild symptoms, and consequently do not seek treatment. In the U.S., those with a history of intravenous drug use, inhaled drug usage, tattoos, or who have been exposed to blood via unsafe sex or social practices are at increased risk of acquiring this disease. Hepatitis C is the leading cause of liver transplantation in the United States.
MiR-122 is a liver specific microRNA, well conserved within vertebrates. MiR-122 is involved in cholesterol metabolism (Esau et al. 2005) and it has recently been shown that miR-122 is important for hepatitis C(HCV) replication (Jopling et al. 2005).
The sequence of miR-122 is well conserved between different mammalian species (mirbase, Sanger Center, UK).
>hsa-miR-122 MIMAT0000421UGGAGUGUGACAAUGGUGUUUG >mmu-miR-122 MIMAT0000246UGGAGUGUGACAAUGGUGUUUG >rno-miR-122 MIMAT0000827UGGAGUGUGACAAUGGUGUUUG >dre-miR-122 MIMAT0001818UGGAGUGUGACAAUGGUGUUUG >xtr-miR-122 MIMAT0003585UGGAGUGUGACAAUGGUGUUUGU >gga-miR-122 MIMAT0001190UGGAGUGUGACAAUGGUGUUUGU >bta-miR-122 MIMAT0003849UGGAGUGUGACAAUGGUGUUUG
Joplin et al. also show that blocking miR-122 by an oligonucleotide inhibits HCV genomic replication. miR-122 interacts with a target sequences in the 5′UTR and 3′UTR of the virus, mutations in these sites reduce virus replication. Both the 5′UTR and 3′UTR miR-122 target site is conserved in the HCV genotypes 1a, 1b, 2, 3, 4, 5, and 6. This suggests that all HCV genotype replication can be reduced by blocking miR-122. It has also recently been shown that genotype 2 replication is blocked by targeting miR-122 with a complementary oligonucleotide (Randall et al. PNAS 2007).
A second cellular factor of importance for the ability of HCV to replicate in mammalian cells is the VLDL assembly pathway (Huang et al. 2007). VLDL assembly is important for packaging/release of the viral particles from the host cell. Reducing the VLDL assembly also reduce release of HCV particles.
One factor of particular significance in the VLDL assembly pathway is Apolipoprotein B (also known as ApoB, apolipoprotein B-100; ApoB-100, apolipoprotein B-48; ApoB-48 and Ag(x) antigen). ApoB is a large glycoprotein that serves an indispensable role in the assembly and secretion of lipids and in the transport and receptor-mediated uptake and delivery of distinct classes of lipoproteins. ApoB plays an important role in the regulation of circulating lipoprotein levels, and is therefore relevant in terms of atherosclerosis susceptibility which is highly correlated with the ambient concentration of apolipoprotein B-containing lipoproteins. See Davidson and Shelness (Annul Rev. Nutr., 2000, 20, 169-193) for further details of the two forms of ApoB present in mammals, their structure and medicinal importance of ApoB.
Two forms of apolipoprotein B exist in mammals. ApoB-100 represents the full-length protein containing 4536 amino acid residues synthesized exclusively in the human liver (Davidson and Shelness, Annul Rev. Nutr., 2000, 20, 169-193). A truncated form known as ApoB-48 is colinear with the amino terminal 2152 residues and is synthesized in the small intestine of all mammals (Davidson and Shelness, Annul Rev. Nutr., 2000, 20, 169-193).
The basis by which the common structural gene for apolipoprotein B produces two distinct protein isoforms is a process known as RNA editing. A site specific cytosine-to-uracil editing reaction produces a UAA stop codon and translational termination of apolipoprotein B to produce ApoB-48 (Davidson and Shelness, Annul Rev. Nutr., 2000, 20, 169-193). +
About 70% of all infected establish chronic infection. Current antiviral therapy against HCV consist of interferon in combination with ribavirin, which is effective in some patients, however a large group do not respond or do not tolerate the treatment. Therefore, a need for novel treatment modalities for HCV exists. The present invention provides a novel combination treatment for HCV, comprising an inhibitor of miR-122 in combination with an inhibitor of ApoB-100 or an inhibitor of the VLDL assembly pathway. The combination treatment provided lead to a reduction of two endogenous host factors miR-122 and the VLDL pathway (or APOB-100) that are needed for the full replication of HCV. Implementation of a treatment that does not directly target the virus, but rather inhibits host factors that are important for HCV replication in the host cell, will reduce the problem related to the high mutation rate of an RNA/RNA replicating virus, which could increase the probability of escape mutations and resistance to therapies that target the virus directly.
The invention relates to the combination of compounds which modulate (suitably inhibit) VLDL assembly, and compounds which inhibit miR-122 function, and that by utilizing both compounds in medical treatment or prevention of HCV infection, an improved treatment is achieved. Whilst not wishing to be bound to any specific theory, we consider that by combating the virus at two different steps in its lifecycle leads to synergy in inhibition and less resistance to drugs.